Letrozole is not chemotherapy, it is a type of hormone therapy that is used to treat people with breast cancer that is hormone receptor-positive. If your cancer is hormone receptor-negative, then letrozole will not be of any benefit. Traditional chemotherapy agents stop cancer cells from growing, dividing, and making more cells. Letrozole works by blocking the action of the enzyme aromatase, which prevents the body from converting androgens into estrogens. Estrogen is a hormone that causes estrogen receptor-positive (ER+) breast cancer to grow. Letrozole belongs to the class of medicines known as aromatase inhibitors.

Letrozole is an oral prescription medication used for the treatment of breast cancer in postmenopausal women. It is usually given after surgery to reduce the risk of breast cancer coming back or spreading and is usually used in addition to chemotherapy and/or radiation treatment. Occasionally, letrozole may be used as the first treatment for breast cancer, for example when surgery isn’t appropriate or needs to be delayed. It may sometimes be given before surgery to shrink a larger breast cancer, and can also be used to treat breast cancer that has come back (recurrence) or spread to another part of the body (secondary breast cancer), often alongside other medications. Femara is the brand name that Novartis uses for its version of letrozole.